Optical position detecting device and recording medium including a detection of dust on a light retro-reflector

ABSTRACT

The position of a light blocking object is detected not only within a display screen, but also outside the display screen. With the use of the function of detecting the position in a region outside the display screen, it becomes possible to provide virtual buttons in this region and detect dust around a light retro-reflector. Dirt on the light retro-reflector is detected based on the levels of light receiving signals of optical units.

This application is a divisional application of U.S. application Ser.No. 10/252,555, filed Sep. 24, 2002 now U.S. Pat. No. 6,844,539, theentire disclosure of which is hereby incorporated herein by reference.U.S. application Ser. No. 10/252,555 is a continuation of PCTInternational Application No. PCT/JP00/02490 which has an Internationalfiling date of Apr. 14, 2000 and which designated the United States ofAmerica.

TECHNICAL FIELD

The present invention relates to an optical position detecting devicefor optically detecting the position of a light blocking object by usingan optical scanning system and a light retro-reflector, and also relatesto a recording medium on which an operational program for the opticalposition detecting device is recorded.

BACKGROUND ART

With the spread of computer systems, mainly personal computers, therehas been used a device for inputting new information or giving variousinstructions to a computer system by pointing at a position on a displayscreen of a display apparatus on which information is displayed by thecomputer system, with an indicating object such as a person's finger ora specific tool. In order to perform an input operation with respect tothe information displayed on the display screen of the display apparatusof a personal computer or the like by a touching method, it is necessaryto detect a touched position (indicated position) on the display screenwith high accuracy.

As one example of a device for detecting such an indicated position onthe display screen that functions as a coordinate surface, JapanesePatent Application Publication No. 62-32491(1987) discloses an opticalposition detecting device. This device comprises: an indicating memberfor pointing at a position on a display screen; at least two opticalscanners for emitting scanning light across the display screen;reflecting means for reflecting the scanning light; and means fordetecting a time at which the scanning light struck the indicatingmember, and detects the position of the indicating member on the displayscreen, based on the relation between the optical scanning start time orend time of the optical scanners and the time at which the scanninglight struck the indicating member.

Besides, another optical position detecting device is disclosed inJapanese Patent Application Laid-Open No. 57-211637(1982). This deviceangularly scans converged light such as a laser beam from the outside ofthe display screen, calculates angles of a position where a special penincluding reflecting means is present from two timings of reflectedlight from the special pen respectively, and detects the coordinates ofthe position from the calculated angles using the triangulationprinciple.

Further, still another optical position detecting device is proposed inJapanese Patent Application Laid-Open No. 62-5428(1987). In this device,light retro-reflectors are positioned as reflecting means on both sideframes of the display screen, return light of an angularly scanned laserbeam from the light retro-reflectors is detected, an angle of a positionwhere a finger or a pen is present is calculated from a timing that thelight beam is blocked by the finger or the pen, and the coordinates ofthe position is detected from the calculated angles using thetriangulation principle.

In an optical position detecting device, when the reflecting means forthe scanning light is dirty or when the reflecting means has dustthereon, a proper detecting operation is not performed. However, none ofthe conventional optical position detecting devices as described abovehas the function to detect such dirt and dust, and thus there is aproblem that operational defects due to such dirt and dust easily occur.

Further, the conventional optical position detecting device includingthe light retro-reflector detects only a position within the displayscreen, and thus has a problem that a region between the display screenand the light retro-reflector can not be used effectively.

The present invention has been made with the aim of solving the aboveproblems, and it is an object of the present invention to provide anoptical position detecting device capable of using the region outsidethe display screen effectively, and a recording medium on which theoperational program for the same is recorded.

Another object of the present invention is to provide an opticalposition detecting device capable of detecting dirt on a lightretro-reflector and/or dust on or around the light retro-reflector, anda recording medium on which the operational program for the same isrecorded.

Still another object of the present invention is to provide an opticalposition detecting device capable of detecting dirt on a lightretro-reflector and/or dust on or around the light retro-reflector andthereby preventing an operational defect caused by such dirt and/ordust, and a recording medium on which the operational program for thesame is recorded.

Yet another object of the present invention is to provide an opticalposition detecting device capable of readily detecting an operationaldefect of an optical scanning unit (polygon mirror) and thereby enablinga stable operation of the position detection process.

A further object of the present invention is to provide an opticalposition detecting device capable of detecting dirt on a cover, coveringan optical transceiver.

DISCLOSURE OF THE INVENTION

In the first aspect, a detection of the position of a light blockingobject is performed not only within a predetermined region (displayscreen), but also in a range outside the predetermined region (a regionbetween the predetermined region and a light retro-reflector) in thesame manner as in the predetermined region. Therefore, the range outsidethe predetermined region can be used effectively, and, for example, avirtual button can be provided in the range.

In the second aspect, dust on or around the light retro-reflector isdetected based on the position of the light blocking object calculatedbased on the results of receiving returned reflected light and thecontinuing time during which the light receiving level is decreased dueto the light blocking object. More specifically, when the calculatedposition of the light blocking object agrees with the position of thelight retro-reflector or is in the vicinity thereof and the decrease inthe light receiving level caused by the light blocking object continuesfor a predetermined time or more, it is judged that dust is present.Accordingly, since dust in the vicinity of the light retro-reflector canbe detected, it is possible to prevent an operational defect caused bythe dust.

In the third aspect, dirt on the light retro-reflector is detected basedon the light receiving level of returned reflected light. Morespecifically, the light retro-reflector is judged to be dirty if thelight receiving level is lower than a level obtained when a lightblocking object is present and higher than a level obtained when noobject is present. Accordingly, since dirt on the light retro-reflectorcan be detected, it is possible to prevent an operational defect causedby the dirt.

In the fourth aspect, when the light receiving level of returnedreflected light attenuates periodically, it is detected that an opticalscanning unit (polygon mirror) has an operational defect. Accordingly,it is possible to take countermeasures promptly and perform the positiondetection process in a stable manner.

In the fifth aspect, when an optical transceiver is covered with acover, dirt on the cover is detected based on the base potential of alight receiving signal of returned reflected light. More specifically,the cover is judged to be dirty if the base potential is higher than apredetermined value. Accordingly, it is possible to prevent anoperational defect caused by the dirt.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1( a) is a front view of an optical position detecting device; FIG.1( b) is a front view of a display apparatus; FIG. 2 is a front viewshowing a state in which the optical position detecting device isexternally mounted on the display apparatus; FIG. 3 is a view showingthe structure and optical path of an optical unit; FIG. 4 is a viewshowing the circuit structure connected to the optical units and theprocessing state of a position detection; FIG. 5 is a block diagramshowing the structure of a controller; FIG. 6 is a schematic diagramshowing the principle of calculating the position and size of a lightblocking object; FIG. 7 is a schematic diagram showing the triangulationprinciple for detecting coordinates; FIG. 8 is a schematic diagramshowing the light blocking object and the blocked range; FIG. 9 is atiming chart showing the relation among the light receiving signal, thescanning angle and the scanning time; FIG. 10 is a schematic diagramshowing the principle of measuring the diameter of a cross section ofthe light blocking object; FIG. 11 is a view showing a state in which alight blocking object (dust) is present on the lower-side lightretro-reflector; FIGS. 12( a) and 12(b) are views showing the lightreceiving signals of the optical units in the state shown in FIG. 11;FIG. 13 is a view showing a state in which a light blocking object(dust) is present on the right-side light retro-reflector; FIGS. 14( a)and 14(b) are views showing the light receiving signals of the opticalunits in the state shown in FIG. 13; FIG. 15 is a view showing anexample of providing virtual buttons; FIG. 16 is a view showing a statein which a template of virtual buttons is attached to the displayapparatus; FIG. 17 is a view showing examples of the shapes of thevirtual buttons; FIG. 18 is a flow chart showing the procedure of theprocess in the optical position detecting device; FIG. 19 is a viewshowing an example of notifying the user of the presence of a lightblocking object on the light retro-reflector; FIG. 20 is a view showinganother example of notifying the user of the presence of a lightblocking object on the light retro-reflector; FIG. 21 is a view showingan example of instructing the user to remove dust; FIG. 22 is a viewshowing another example of instructing the user to remove dust; FIG. 23is a view showing a state in which the light retro-reflector has dirt;FIGS. 24( a) and 24(b) are views showing the light receiving signals ofthe optical units in the state shown in FIG. 23; FIG. 25 is a flow chartshowing the procedure of the process of detecting dirt on the lightretro-reflector; FIG. 26 is a view showing an example of instructing theuser to clean the light retro-reflector; FIG. 27 is a view showing anexample of the light receiving signals of the optical units inassociation with four scanning surfaces of the polygon mirror; FIG. 28is a view showing a state in which the optical units are provided with acover; FIGS. 29( a) and 29(b) are views showing the light receivingsignals of the optical units in the state shown in FIG. 28; FIG. 30 is aflow chart showing the procedure of the process of detecting dirt on thesurface of the cover; FIG. 31 is a view showing an example ofinstructing the user to clean the cover; and FIG. 32 is a view showingthe structure of an embodiment of a recording medium.

BEST MODE FOR IMPLEMENTING THE INVENTION

The following description will describe the present invention in detailwith reference to the drawings illustrating some embodiments thereof.

FIG. 1( a) is a front view of an optical position detecting device. Thisoptical position detecting device 1 as a whole is in the form of ahollow rectangular parallelepiped body with no rid and bottom, andcomprises four side frames 1 a, 1 b, 1 c and 1 d. In FIG. 1( a), theupper side frame 1 a has a larger width compared to other three sideframes 1 b, 1 c and 1 d, and incorporates optical units 10 a and 10 bhaving a later-described internal structure in both ends thereof.Moreover, the three side frames 1 b, 1 c and 1 d are provided with lightretro-reflectors 4.

FIG. 1( b) is a front view of a display apparatus, and the flatparallelepiped display apparatus 20 comprises a display screen 21 and ascreen frame 22 on which the display screen 21 is mounted. The opticalposition detecting device 1 having the above-described structure isexternally mounted on such a display apparatus 20. FIG. 2 is a frontview showing a state in which the optical position detecting device 1 isexternally mounted on the display apparatus 20.

FIG. 3 is a view showing the structure of optical units 10 a, 10 b andthe optical path. Both of the optical units 10 a and 10 b have the sameinternal structure. The optical unit 10 a (10 b) includes a lightemitting element 11 composed of a laser diode (LD) for emitting infraredlaser light; a collimation lens 12 for making the laser light from thelight emitting element 11 parallel light; a light receiving element 13composed of a photodiode (PD) for receiving reflected light from thelight retro-reflector 4; a light blocking member 14 having an aperture14 a for limiting the incident light on the light receiving element 13;a polygon mirror 15 having the shape of a square column, for example,for angularly scanning the laser light from the light emitting element11; an aperture mirror 16 for limiting light to be projected from thecollimation lens 12 to the polygon mirror 15 by an aperture 16 a and forreflecting light reflected from the light retro-reflector 4 through thepolygon mirror 15 toward the light receiving element 13; a condenserlens 17 for focusing the reflected light from the aperture mirror 16; amotor 18 for rotating the polygon mirror 15; and an optical unit mainbody 19 on which these members are mounted and fixed.

After the laser light emitted from the light emitting element 11 is madeparallel light by the collimation lens 12 and passes through theaperture 16 a of the aperture mirror 16, it is angularly scanned in aplane substantially orthogonal to the side frames 1 a, 1 b, 1 c and 1 dof the optical position detecting device 1 with the rotation of thepolygon mirror 15, and then projected onto the light retro-reflector 4.After the reflected light from the light retro-reflector 4 is reflectedby the polygon mirror 15 and the aperture mirror 16, it is focused bythe condenser lens 17, passes through the aperture 14 a of the lightblocking member 14, and enters the light receiving element 13. However,if an object is present in the path of the scanning light, the scanninglight is blocked, and therefore the reflected light does not enter thelight receiving element 13.

FIG. 4 is a view showing the circuit structure connected to the opticalunits 10 a, 10 b and the processing state of position detection.

Connected to the optical units 10 a and 10 b are light emitting elementdrivers 32 a and 32 b for driving the respective light emitting elements11; light receiving signal detectors 33 a and 33 b for converting thequantity of light received by the respective light receiving elements 13into electric signals; and a polygon controller 34 for controlling theoperations of the respective polygon mirrors 15.

The controller 35 transmits drive control signals to the light emittingelement drivers 32 a and 32 b. According to the drive control signals,the light emitting element drivers 32 a and 32 b are driven, and thelight emitting operations of the respective light emitting elements 11are controlled. The light receiving signal detectors 33 a and 33 btransmit the light receiving signals of the reflected light of therespective light receiving elements 13 to the controller 35. Based onthe light receiving signals from the respective light receiving elements13, the controller 35 performs the process of calculating the positionand size of a light blocking object S, such as a finger and a pen, theprocess of detecting dirt on the light retro-reflector 4, the process ofdetecting dust around the light retro-reflector 4, etc. and alsocontrols the overall operations of the device.

FIG. 5 is a structural diagram of the controller 35. The controller 35includes a CPU 41, a ROM 42, a RAM 43, and a display interface 44. TheCPU 41 is connected with these hardware parts and controls them, andalso performs various software functions according to computer programsstored in the ROM 42. On the ROM 42, various software programs necessaryfor performing the operations of the processes of the optical positiondetecting device were stored beforehand. The RAM 43 is composed of SRAM,or flash memory or the like, and stores temporary data generated duringthe execution of software, threshold levels necessary for executing thesoftware, etc. Besides, the display interface 44 controls the display ofmessages on the display apparatus 20 directed to the user.

Next, the following description will explain the position detectionoperation. As shown in FIG. 4, if the explanation is given with respectto the optical unit 10 b, for example, the projected light from theoptical unit 10 b is scanned in a counterclockwise direction on FIG. 4from a position where the projected light directly enters its lightreceiving element 13 to a position (Ps) where the projected light isreflected by an end of the light retro-reflector 4, that is, a scanningstart position. Then, the projected light is reflected by the lightretro-reflector 4 until it comes to a position (P1) where the projectedlight reaches one end of the light blocking object S, but the projectedlight is blocked by the light blocking object S up to a position (P2)where it reaches the other end of the light blocking object S, and thenthe projected light is reflected by the light retro-reflector 4 until itcomes to a scanning end position (Pe).

Next, the following description will explain specific operations forcalculating the position and size of the light blocking object S. FIG. 6is a schematic diagram showing the calculation principle. In FIG. 6,however, illustration of the component members other than the opticalunits 10 a, 10 b, light retro-reflector 4 and display screen 21 isomitted. Further, FIG. 6 shows an example in which a finger is used asthe light blocking object S.

The controller 35 controls the polygon controller 34 to rotate therespective polygon mirrors 15 in the optical units 10 a and 10 b, andthereby angularly scanning the laser light from the respective lightemitting elements 11. As a result, the reflected light from the lightretro-reflector 4 enters the respective light receiving elements 13. Thequantity of the received light that entered the respective lightreceiving elements 13 as mentioned above is obtained as the lightreceiving signals which are the outputs of the light receiving signaldetectors 33 a and 33 b.

Besides, in FIG. 6, θ00 and φ00 represent the angles from a referenceline that connects the two optical units 10 a and 10 b together to thelight receiving elements, respectively; θ0 and φ0 represent the anglesfrom the reference line connecting the two optical units 10 a and 10 btogether to the ends of the light retro-reflector 4; θ1 and φ1 representthe angles from the reference line to one end of the light blockingobject S on the reference line side; and θ2 and φ2 represent the anglesfrom the reference line to the other end of the light blocking object Son the side opposite to the reference line.

If the light blocking object S is present on the optical path of thescanning light on the display screen 21, the light projected from theoptical units 10 a and 10 b and then reflected by the light blockingobject S does not enter the respective light receiving elements 13.Therefore, in a condition as shown in FIG. 6, the reflected light doesnot enter the light receiving element 13 in the optical unit 10 a whenthe scanning angle is in a range between 0° and θ0; the reflected lightenters the light receiving element 13 when the scanning angle is in arange between θ0 and θ1; and the reflected light does not enter thelight receiving element 13 when the scanning angle is in a range betweenθ1 and θ2. Similarly, the reflected light does not enter the lightreceiving element 13 in the optical unit 10 b when the scanning angle isin a range between 0° and φ0; the reflected light enters the lightreceiving element 13 when the scanning angle is in a range between φ0and φ1, and the reflected light does not enter the light receivingelement 13 when the scanning angle is in a range between φ1 and φ2.

Next, the following description will explain the process of calculatingcoordinates of a central position (indicated position) of the lightblocking object S (a finger in this example) from the blocked rangecalculated in the above-mentioned manner. First, conversion of anglesinto orthogonal coordinates based on the triangulation will beexplained. As shown in FIG. 7, the position of the optical unit 10 a isset as an origin O, the upper side and left side of the display screen21 are set as the X-axis and Y-axis, and the length of the referenceline (the distance between the optical units 10 a and 10 b) is set as L.Moreover, the position of the optical unit 10 b is set as B. When acentral point P (Px, Py) indicated by the light blocking object S on thedisplay screen 21 is positioned at angles θ and φ from the optical units10 a and 10 b to the X-axis, the values of the X-coordinate Px and theY-coordinate Py of the point P can be calculated according to theprinciple of triangulation as shown by the following equations (1) and(2), respectively.Px(θ, φ)=(tan φ)÷(tan θ+tan φ)×L  (1)Py(θ, φ)=(tan θ·tan φ)÷(tan θ+tan φ)×L  (2)

By the way, since the light blocking object S (finger) has dimensions,when the detection angles in the timings of rise/fall of the detectedlight receiving signals are used, as shown in FIG. 8, four points (P1through P4 in FIG. 8) on the edge of the light blocking object S(finger) are detected. These four points are all different from theindicated central point (Pc in FIG. 8). Therefore, the coordinates (Pcx,Pcy) of the central point Pc are calculated as follows. Pcx and Pcy canbe expressed as shown by the following equations (3) and (4),respectively.Pcx(θ, φ)=Pcx(θ1+dθ/2, φ1+dφ/2)  (3)Pcy(θ, φ)=Pcy(θ1+dθ/2, φ1+dφ/2)  (4)

Then, by substituting θ1+dθ/2 and φ1+dφ/2 expressed by equations (3) and(4) for θ and φ of equations (1) and (2) above, the coordinates of theindicated central point Pc can be obtained.

Note that, in the above-mentioned example, the average values of theangles are first calculated and then substituted into the convertingequations (1) and (2) of triangulation so as to calculate thecoordinates of the central point Pc as the indicated position. However,it is also possible to calculate the coordinates of the central point Pcby first calculating the rectangular coordinates of the four points P1through P4 from the scanning angles according to the convertingequations (1) and (2) of triangulation and then calculating the averageof the calculated coordinate values of the four points. Further, it isalso possible to determine the coordinates of the central point Pc, thatis, the indicated position by considering parallax and easiness to seethe indicated position.

By the way, when the scanning angular velocity of each polygon mirror 15is constant, the information about the scanning angle can be obtained bymeasuring a time. FIG. 9 is a timing chart showing the relation betweenthe light receiving signal from the light receiving signal detector 33 aand the scanning angle θ and scanning time T of the polygon mirror 15 inthe optical unit 10 a. When the scanning angular velocity of the polygonmirror 15 is constant, if the scanning angular velocity is denoted as ω,then a proportional relation as shown by equation (5) below isestablished between the scanning angle θ and the scanning time T.θ=ω×T  (5)

Therefore, the angles θ1 and θ2 at the time of fall and rise of thelight receiving signal establish the relations shown by equations (6)and (7) below with the scanning time t1 and t2.θ1=ω×t1  (6)θ2=ω×t2  (7)

Thus, when the scanning angular velocity of the polygon mirrors 15 isconstant, it is possible to measure the blocked range and coordinateposition of the light blocking object S (finger) by using the timeinformation.

In addition, it is also possible to calculate the size (the diameter ofa cross section) of the light blocking object S (finger) from themeasured blocked range. FIG. 10 is a schematic diagram showing theprinciple of measuring the diameter of a cross section of the lightblocking object S. In FIG. 10, D1 and D2 represent diameters of thecross sections of the light blocking object S seen from the opticalunits 10 a and 10 b, respectively. First, distances OPc (r1) and BPc(r2) from the positions O (0, 0) and B (L, 0) of the optical units 10 aand 10 b to the central point Pc (Pcx, Pcy) of the light blocking objectS are calculated as shown by equations (8) and (9) below.OPc=r1=(Pcx ² +Pcy ²)^(1/2)  (8)BPc=r2={(L−Pcx)² +Pcy ²}^(1/2)  (9)

Since the radius of the cross section of the light blocking object S canbe approximated by the product of the distance to the central point andthe sine of a half of the blocking angle, the diameters D1 and D2 of thecross sections are measurable according to equations (10) and (11)below.

$\begin{matrix}{{D1} = {{2 \cdot {r1} \cdot {\sin( {d\;{\theta/2}} )}}\mspace{34mu} = {2{( {{Pcx}^{2} + {Pcy}^{2}} )^{1/2} \cdot {\sin( {d\;{\theta/2}} )}}}}} & (10) \\{{D2} = {{2 \cdot {r2} \cdot {\sin( {d\;{\phi/2}} )}}\mspace{34mu} = {2{\{ {( {L - {Pcx}} )^{2} + {Pcy}^{2}} \}^{1/2} \cdot {\sin( {d\;{\phi/2}} )}}}}} & (11)\end{matrix}$

Note that, when dθ/2, dφ/2≈0, it is possible to approximatesin(dθ/2)≈dθ/2≈tan(dθ/2) and sin(dφ/2)≈dφ/2≈tan(dφ/2), and thereforedθ/2 or tan(dθ/2), or dφ/2 or tan(dφ/2) may be substituted for sin(dθ/2)and sin(dφ/2) in equations (10) and (11).

By the way, as shown in FIG. 4, the laser light from the optical units10 a and 10 b can scan not only the region within the display screen 21,but also the region outside thereof, i.e., the region between thedisplay screen 21 and the light retro-reflector 4, and the reflectedlight from the light retro-reflector 4 can be received by the opticalunits 10 a and 10 b. Hence, even when a light blocking object is presentin such a region, it is possible to calculate the position in exactlythe same manner as the position within the display screen 21. Moreover,by inputting/setting the size information and positional informationabout the display screen 21 in advance, it is possible to readily judgeas to whether the light blocking object is present within the displayscreen 21 or outside the display screen 21. The following descriptionwill explain an example utilizing the detection of the light blockingobject in the region outside the display screen 21 and the calculationof the position (the detection of dust and the use of virtual buttons).

First, the detection of a light blocking object present on or around thelight retro-reflector 4 will be explained. FIG. 11 is a view showing astate in which the light blocking object S is present on the lightretro-reflector 4 on the lower-side frame 1 c. FIGS. 12( a) and 12(b)show, respectively, the light receiving signals of the optical units 10a and 10 b in such a state. Further, FIG. 13 is a view showing a statein which the light blocking object S is present on the lightretro-reflector 4 on the right-side frame 1 d. FIGS. 14( a) and 14(b)show, respectively, the light receiving signals of the optical units 10a and 10 b in such a state. Note that the broken lines in FIG. 12 andFIG. 14 indicate a threshold level for detecting the light blockingobject, and, when the light receiving signal level becomes lower thanthis threshold level within the scanning range, the presence of thelight blocking object is detected.

When there is a light blocking object S on the light retro-reflector 4on the lower-side frame 1 c, the light blocking object S is detected byboth of the optical units 10 a and 10 b, while, when there is a lightblocking object S on the light retro-reflector 4 on the right-side frame1 d, the light blocking object S is detected only by the optical unit 10a because the laser light from the optical unit 10 b is not scanned tothe region. Note that, when there is a light blocking object S on thelight retro-reflector 4 on the left-side frame 1 b, the light blockingobject S is detected only by the optical unit 10 b.

Thus, by inputting/setting the positional information about the opticalunits 10 a, 10 b and the light retro-reflectors 4 in advance, it ispossible to detect which side-frame light retro-reflector 4 has thelight blocking object thereon or nearby, based on the calculatedposition of the light blocking object.

Next, an example of using the virtual buttons will be explained. FIG. 15is a view showing an example of the arrangement of the virtual buttons.Virtual buttons 51 for accepting specific functions from outside areprovided in a region located outside the display screen 21 and capableof detecting the position of the light blocking object. Hence, thevirtual buttons 51 enable the effective use of the outside of thedisplay screen 21, and can also be used as hidden command input means.The user can input a desired command by pressing the virtual button 51.

FIG. 16 is a view showing a state in which a template 52 of the virtualbuttons 51 is attached to the display apparatus 20 so as to improve theuser interface. A thin template 52 is preferred so as not to interferewith the scanning light. The display apparatus 20 may be provided with arecessed section in advance so as to fit the template 52 in the recessedsection.

Note that, in FIGS. 15 and 16, although the virtual buttons 51 areprovided on the upper and lower outside of the display screen 21,needless to say, it is also possible to provide the virtual buttons 51on the left and right outside thereof.

FIG. 17 is a view showing examples of the shapes of such virtual buttons51. Since the position of the light blocking object is calculated usingthe triangulation principle, if a virtual button (virtual button 51 a inFIG. 17) is provided in between the two optical units 10 a and 10 b orthe vicinity thereof, the position calculation accuracy in thehorizontal direction is lowered. Therefore, the shape of the virtualbutton 51 a is made longer in the horizontal direction so as to enablestable detection of the pressing of the button. Besides, for the samereason, in the case where virtual buttons (virtual buttons 51 b in FIG.17) are provided on the side opposite to the optical units 10 a and 10 bwith the display screen 21 therebetween, at positions in the vicinity ofboth ends of the display apparatus 20, the position detection accuracyin the vertical direction is lowered. Therefore, the shape of thevirtual button 51 b is made longer in the vertical direction so as toenable stable detection of the pressing of the button.

FIG. 18 is a flow chart showing the procedure of the process in theoptical position detecting device of the present invention. First, theCPU 41 detects a light blocking object and calculates the positionthereof (step S1). The CPU 41 judges whether the calculated position ofthe light blocking object is within the display screen 21 (step S2). Ifit is within the display screen 21 (S2: YES), the CPU 41 performs adrawing process based on an indicated input given by input means (forexample, a finger) (step S7).

Next, the CPU 41 judges whether the calculated position of the lightblocking object is on or around the light retro-reflector 4 (step S3).If not (S3: NO), the CPU 41 judges whether the calculated positioncoincides with the position of a virtual button 51 (step S8). If itcoincides with the position of a virtual button 51 (S8: YES), the CPU 41judges that the virtual button 51 is indicated by the input means (forexample, a finger) and executes the process of the virtual button 51(step S9). If the calculated position does not coincide with theposition of a virtual button 51 (S8: NO), since it is considered thatthe user made a touch by mistake, the CPU 41 just ends the process.

If the calculated position of the light blocking object is on or aroundthe light retro-reflector 4 (S3: YES), the CPU 41 notifies the user ofthis fact (step S4). FIG. 19 is a view showing an example ofnotification, notifying the user of this fact by displaying thepositional information together with a message “A light blocking objectis present on the light retro-reflector” on the display screen 21. FIG.20 is a view showing another example of notification, displaying amessage notifying the presence of the light blocking object and theposition of the light blocking object with an arrow. Accordingly, it ispossible to attract the user's attention to the presence of an objectother than the input means (for example, a finger) on or around thelight retro-reflector 4.

Next, the CPU 41 judges whether the light blocking object has beenpresent on or around the light retro-reflector 4 for a predeterminedtime or more (for example, one minute or more) (step S5). If it has beenpresent for the predetermined time or more (S5: YES), the CPU 41 judgesthat the light blocking object is dust and instructs the removal of thedust (step S6). FIG. 21 is a view showing an example of instruction,notifying the user of the presence of the dust by displaying on thedisplay screen 21 a message “Remove dust on the light retro-reflector”together with the positional information. FIG. 22 is a view showinganother example of instruction, indicating the position of dust with anarrow as well as displaying the dust removal message. Accordingly, thepresence of dust is notified to the user, and the dust is promptlyremoved, thereby preventing an operational defect caused by dust.

Note that, if the light blocking object disappeared within thepredetermined time (S5: NO), since it is considered that the user made atouch by mistake, the CPU 41 ends the displaying of the messageindicating the presence of the light blocking object (step S10).

Besides, in the above-described example, although dust on or around thelight retro-reflector 4 and the pressing of the virtual button 51 aredistinguished based on the calculated position, it is also possible todistinguish them based on the light blocking time. More specifically,when the light blocking time is equal to or more than a predeterminedtime, the CPU 41 judges that dust is present on or around the lightretro-reflector 4, while, when the light blocking time is shorter thanthe predetermined time, the CPU 41 judges that the virtual button 51 ispressed.

Next, the following description will explain an embodiment for detectingdirt on the light retro-reflector 4. FIG. 23 is a view showing a statein which the light retro-reflector 4 on the lower side frame 1 c hasdirt D. FIGS. 24( a) and 24(b) are views showing the light receivingsignals of the optical units 10 a and 10 b in such a state. Note thatthe broken lines in FIG. 24 indicate a threshold level for detecting alight blocking object similar to that of FIG. 12 and FIG. 14, while thedotted lines in FIG. 24 indicate a dirt detection level necessary fordetecting the dirt on the light retro-reflector 4. The dirt detectionlevel is higher than the threshold level.

FIG. 25 is a flow chart showing the procedure of the process ofdetecting dirt on the light retro-reflector 4. The CPU 41 judges whetherthe light receiving signal level became lower than the threshold levelwithin the scanning range (step S1). If it became lower than thethreshold level (S11: YES), the CPU 41 judges that a light blockingobject is present (step S15). If it did not become lower the thresholdlevel (S11: NO), the CPU 41 judges whether the light receiving signallevel became lower than the dirt detection level within the scanningrange (step S12).

If the light receiving signal level became lower than the dirt detectionlevel within the scanning range (S12: YES), the CPU 41 detects that thelight retro-reflector 4 has dirt and calculates the position of the dirt(step S13). Then, the CPU 41 instructs the user to clean the lightretro-reflector 4 (step S14). FIG. 26 is a view showing an example ofinstruction, notifying the user of the presence of dust by displaying onthe display screen 21 a message “Clean the light retro-reflector”together with the positional information. Accordingly, the user isnotified of the fact that there is dirt on the light retro-reflector 4,and then the light retro-reflector 4 is promptly cleaned, therebypreventing an operational defect due to the dirt.

Note that, after the process of S15 in FIG. 25, by connecting theprocesses of S1 through S10 shown in FIG. 18 together, it is possible tosequentially execute the proper drawing process, the process ofdetecting dirt on the light retro-reflector 4, the process of detectingthe pressing of the virtual button and the process of detecting dust onor around the light retro-reflector 4.

Next, the following description will explain an embodiment for detectinga deviation of scanning light of the polygon mirror 15. FIG. 27 is aview showing an example of the light receiving signals of the opticalunits 10 a and 10 b in association with the four scanning surfaces ofthe polygon mirror 15. The light receiving signal levels become lowerthan the threshold level periodically, and, in FIG. 27, the only lightreceiving signal level corresponding to the third scanning surface ofthe polygon mirror 15 is lower than the threshold level.

Since the surface inclination angles of the polygon mirror 15 are notequal, if the scanning light gets out of the light retro-reflector 4, noreflected light is obtained and a pattern as shown in FIG. 27 isexhibited. Accordingly, when a change in the light receiving signals inwhich the signal level became lower than the threshold levelperiodically was detected, it is possible to judge that there is anoperational defect of the polygon mirror 15.

In the case where such an operational defect of the polygon mirror 15was detected, the calculation data can be stabilized by performing thesmoothing process of calculating the movement average and removing themaximum and minimum values by using software for calculating theposition of the light blocking object.

Next, the following description will explain an embodiment for detectingdirt on the surface of a cover provided for the optical units 10 a and10 b. FIG. 28 is a view showing a state in which the optical units 10 aand 10 b are provided with a cover 53 to prevent dust or the like fromentering into the optical units 10 a and 10 b from outside.

FIG. 29 shows examples of the light receiving signals of the opticalunits 10 a and 10 b in such a state. FIG. 29( a) shows the lightreceiving signal when the surface of the cover 53 is not dirty, whileFIG. 29( b) shows the light receiving signal when the surface of thecover 53 is dirty. Note that the broken lines in FIG. 29 indicate athreshold level for detecting a light blocking object, while the dottedlines show a reference potential necessary for detecting dirt on thesurface of the cover 53.

When the surface of the cover 53 is not dirty, the base potential is nothigh. On the other hand, when it is dirty, the base potential of thelight receiving signal is increased due to irregular reflection from thedirt. Accordingly, by detecting such an increase in the base potential,it is possible to detect the dirt on the surface of the cover 53.

FIG. 30 is a flow chart showing the procedure of the process ofdetecting dirt on the surface of the cover 53. The CPU 41 measures thebase potential of the obtained light receiving signal (step S21), andjudges whether the measured value is higher than the reference potential(step S22). If it is higher (S22: YES), the CPU 41 detects the presenceof dirt on the surface of the cover 53 (step S23), and instructs theuser to clean the cover 53 (step S24). FIG. 31 is a view showing anexample of instruction, notifying the user of the presence of dirt bydisplaying a message “Clean the cover” on the display screen 21.Accordingly, the presence of dirt on the surface of the cover 53 isnotified to the user, and the cover 53 is promptly cleaned, therebypreventing an operational defect caused by the dirt. On the other hand,if the measured base potential is not higher than the referencepotential (S22: NO), the CPU 41 judges that the surface of the cover 53is not dirty (step S25).

Note that it is of course possible to sequentially execute theabove-mentioned processes of S21 through S25 shown in FIG. 30 byconnecting them with the flow chart shown in FIG. 18 and/or FIG. 25.

FIG. 32 is a view showing the structure of an embodiment of a recordingmedium of the present invention. A program exemplified here includes apart or all of the above-mentioned processes of calculating the positionand size of a light blocking object and the processes in the flow chartsshown in FIGS. 18, 25 and 30, and is recorded on recording mediaexplained below.

In FIG. 32, a recording medium 61 to be on-line connected to a computer60 is implemented using a server computer, for example, WWW (World WideWeb), located in a place distant from the installation location of thecomputer 60, and a program 61 a as mentioned above is recorded on therecording medium 61. The program 61 a read from the recording medium 61controls the computer 60 so that the computer 60 executes theabove-described processes.

A recording medium 62 provided inside the computer 60 is implementedusing, for example, a hard disk drive or a ROM (equivalent to ROM 42 inFIG. 5) installed in the computer 60, and a program 62 a as mentionedabove is recorded on the recording medium 62. The program 62 a read fromthe recording medium 62 controls the computer 60 so that the computer 60executes the above-described processes.

A recording medium 63 used by being loaded into a disk drive 60 ainstalled in the computer 60 is implemented using, for example, aremovable magneto-optical disk, CD-ROM, flexible disk or the like, and aprogram 63 a as mentioned above is recorded on the recording medium 63.The program 63 a read from the recording medium 63 controls the computer60 so that the computer 60 executes the above-described processes.

Note that while the above examples illustrate the detection carried outby the optical position detecting device externally mounted on thedisplay apparatus, it is of course possible to apply the presentinvention in a similar manner to a display screen-integrated opticalposition detecting device.

INDUSTRIAL APPLICABILITY

As described above, since the present invention performs detection ofthe position of a light blocking object not only within a predeterminedregion (display screen), but also in a range outside the predeterminedregion in the same manner as in the predetermined region, the rangeoutside the predetermined region can also be used effectively. Moreover,since the present invention can detect dust on or around the lightretro-reflector and/or dirt on the light retro-reflector, it is possibleto prevent an operational defect caused by the dust and/or dirt.Furthermore, the present invention can readily detect an operationaldefect of the optical scanning unit (polygon mirror) and perform theoperation of the position detection process in a stable manner. Inaddition, since the present invention can detect dirt on a covercovering the optical transceivers, it is possible to prevent anoperation defect caused by the dirt.

1. An optical position detecting device comprising: a lightretro-reflector provided outside a predetermined region; at least twooptical transceivers, each including an optical scanning unit forangularly scanning light in a plane substantially parallel to thepredetermined region and a light receiving unit for receiving reflectedlight from a portion of said light retro-reflector irradiated with thescanning light; and a detector for detecting presence of a lightblocking object in a region optically scanned by said optical scanningunits when a level of light received by said light receiving unit islower than a predetermined first level and for detecting a position ofthe light blocking object based on scanning angles of said opticalscanning units in this scanning, said optical position detecting devicebeing characterized by further comprising: a comparing unit forcomparing the level of light received by said light receiving unit witha second level higher than the first level; and a judging unit formaking a judgment that said light retro-reflector is dirty when thelevel of light received by said light receiving unit is higher than thefirst level and lower than the second level.
 2. A computer-readablerecording medium having a program recorded thereon for an opticalposition detecting device comprising: a light retro-reflector providedoutside a predetermined region; and at least two optical transceivers,each including an optical scanning unit for angularly scanning light ina plane substantially parallel to the predetermined region and a lightreceiving unit for receiving reflected light from a portion of saidlight retro-reflector irradiated with the scanning light, the programcausing a computer to detect dirt on said light retro-reflector, saidrecording medium being characterized in that the program includesprogram code means for causing the computer to make a comparison betweena level of light received by said light receiving unit and apredetermined first level and a predetermined second level higher thanthe first level; and program code means for causing the computer to makea judgment that said light retro-reflector is dirty when the level oflight received by said light receiving unit is higher than the firstlevel and lower than the second level.
 3. A computer-readable recordingmedium having a program recorded thereon for an optical positiondetecting device comprising: a light retro-reflector provided outside apredetermined region; and at least two optical transceivers, eachincluding an optical scanning unit for angularly scanning light in aplane substantially parallel to the predetermined region and a lightreceiving unit for receiving reflected light from a portion of saidlight retro-reflector irradiated with the scanning light, the programcausing a computer to detect dust on or around said lightretro-reflector, said recording medium being characterized in that theprogram includes program code means for causing the computer to executedetection of a light blocking object present in a region opticallyscanned by said optical scanning units when a level of light received bysaid light receiving unit is lower than a predetermined level; programcode means for causing the computer to execute calculation of a positionof the light blocking object based on scanning angles of said opticalscanning units and results of receiving light by said light receivingunits; and program code means for causing the computer to detect dust onor around said light retro-reflector based on a time during which thelevel of light received by said light receiving unit is lower than thepredetermined level and the calculated position of the light blockingobject.